U.S. patent number 4,308,970 [Application Number 06/101,220] was granted by the patent office on 1982-01-05 for plastic bucket defining annular inwardly projecting ridge.
Invention is credited to John W. Von Holdt.
United States Patent |
4,308,970 |
Von Holdt |
January 5, 1982 |
Plastic bucket defining annular inwardly projecting ridge
Abstract
A plastic bucket having a lip which defines means for engaging a
bucket lid in sealing relation. The interior wall of the bucket
defines an annular, inwardly projecting ridge spaced from the lip.
The ridge extends around the inner circumference of the bucket, and
defines an annular, inwardly pointed apex, to provide increased
hoop strength to the bucket adjacent to its mouth and to provide an
internal brush wiping member within the bucket.
Inventors: |
Von Holdt; John W. (Niles,
IL) |
Family
ID: |
22283569 |
Appl.
No.: |
06/101,220 |
Filed: |
December 7, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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963736 |
Nov 27, 1978 |
4210258 |
|
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Current U.S.
Class: |
220/790 |
Current CPC
Class: |
B29C
45/43 (20130101); B65D 43/0208 (20130101); B65D
1/46 (20130101); B65D 2543/00898 (20130101); B65D
2543/00092 (20130101); B65D 2543/00296 (20130101); B65D
2543/0037 (20130101); B65D 2543/00472 (20130101); B65D
2543/005 (20130101); B65D 2543/00509 (20130101); B65D
2543/00518 (20130101); B65D 2543/00537 (20130101); B65D
2543/00555 (20130101); B65D 2543/00629 (20130101); B65D
2543/00648 (20130101); B65D 2543/00685 (20130101); B65D
2543/0074 (20130101); B65D 2543/00759 (20130101); B65D
2543/00796 (20130101); B65D 2543/00888 (20130101) |
Current International
Class: |
B29C
45/43 (20060101); B65D 43/02 (20060101); B65D
1/46 (20060101); B65D 1/40 (20060101); B65D
039/00 () |
Field of
Search: |
;220/306,307 ;206/508
;150/5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hall; George T.
Attorney, Agent or Firm: Pigott, Jr.; Charles F. Ellis;
Garrettson
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. application Ser.
No. 963,736, filed Nov. 27, 1978; now U.S. Pat. No. 4,210,258.
Claims
That which is claimed is:
1. A plastic bucket having a lip at its mouth, said lip defining
means for engaging a bucket lid in sealingly secured relation to
said lip, the improvement comprising, in combination:
the interior wall of said bucket defining an annular, inwardly
projecting ridge positioned adjacent to but spaced from said lip,
said ridge extending around the inner circumference of said bucket
and defining an annular, inwardly-pointed apex, to provide
increased hoop strength to said bucket adjacent its mouth.
2. The bucket of claim 1 in which said annular apex is positioned
less than one inch from the outermost portion of the bucket lip,
and said annular apex is essentially linear.
3. The bucket of claim 2 in which the surfaces of said
inwardly-projecting ridge extending from the annular apex to the
interior wall of the bucket are concave in shape.
4. A plastic bucket having a lip at its mouth, a plastic bucket lid
in sealingly secured relation to the lip of said bucket, the
improvement comprising, in combination: the interior wall of said
bucket defining an annular, inwardly-projecting ridge positioned
adjacent to but spaced from said lip, said ridge extending around
the inner circumference of said bucket and defining an annular,
inwardly-pointed apex, said lid defining first and second
transversely extending annular walls forming an annular open
depression, said second annular wall defining the outer limit of
said depression, said first annular wall defining the inner limit
of said depression and constituting an integral segment of the
bucket lid, being connected at opposed sides to other portion of
the bucket lid, and a third transversely-extending annular wall
positioned outwardly from said second annular wall, said second and
third annular walls, in turn, defining between them an annular
locking slot which receives and holds the lip of said bucket, said
second wall also carrying an outwardly-positioned annular
projection defining a surface which faces the annular locking slot
and which defines an angle to the plane of said second annular
wall, said annular projection being in contacting and retaining
relation with a mating projection of said bucket lip positioned
within the locking slot, the second wall also defining, below said
outwardly-positioned annular projection, a surface which is of a
shape complimentary to the shape of the side of said annular ridge
which faces the mouth of said bucket, to form an annular, abutting
sealing surface between said outer side of the ridge and the second
wall and extending essentially to said apex, said third annular
wall defining an inwardly-positioned projection adapted to
interlock with an outwardly facing projection of said bucket lip,
positioned within the locking slot, said first annular wall being
adapted for preferentially flexing upon shock adjacent the bucket
lip, causing said second wall to remain relatively immovable under
such circumstances for improved sealing strength.
5. The bucket of claim 4 in which the surface of said
inwardly-projecting ridge extending from the annular apex to the
interior wall and facing said bucket mouth is concave in shape, and
the mating surface of said second wall of the bucket lid is
correspondingly convex in shape.
6. The plastic bucket and lid of claim 4 in which said first wall
of the bucket lid defines the outer surface of an annular groove
defined in said lid.
7. The bucket and lid of claim 4 in which said lip of the bucket
defines an outwardly pointing annular ridge terminating in an
outwardly-pointing annular apex, a surface of said bucket lip which
extends outwardly, relative to said bucket mouth, defining a
generally planar annular surface, adapted relative to the shape of
the inner surface of said bucket lip to permit the parting line for
said bucket lip to be located at a position elsewhere than said
generally planar surface and the outer end of said bucket lip while
permitting easy removal from a mold.
8. The bucket and lid of claim 7 in which a mold parting line for
said bucket is located at said outwardly-projecting apex of the
bucket lip.
9. The bucket and lid of claim 4 in which said second annular wall
is thicker than said first annular wall.
10. A plastic bucket having a lip at its mouth, said lip defining
means for engaging a bucket lid in sealingly secured relation to
said lip, the improvement comprising, in combination:
the interior wall of said bucket defining an annular,
inwardly-projecting ridge positioned adjacent to but spaced from
said lip, said ridge extending around the inner surface of said
bucket and defining an annular, inwardly-pointed apex, to provide
increased hoop strength to said bucket adjacent its mouth, said
bucket lip also defining an annular, outwardly-projecting ridge
extending around the outer circumference of said bucket lip and
defining an annular, outwardly pointing apex, a surface of said
bucket lip extending outwardly relative to the direction of said
bucket mouth from said apex, being of generally planar, annular
shape, said generally planar, annular surface and the outer end of
said bucket lip being free of mold parting line marks for improved
sealing characteristics.
11. The bucket of claim 10 in which a mold parting line mark is
positioned at the outwardly-pointing, annular apex of the bucket
lip.
12. The bucket of claim 10 in which a bucket lid is sealingly
secure to said lip, said bucket lid defining inner and outer
transverse annular walls to further define an annular locking slot
therebetween, said outer wall defining an annular
inwardly-extending projection removably engaging said outwardly
projecting ridge, said inner wall defining an annular
outwardly-facing projection for engaging an inner portion of said
bucket lip.
13. The bucket of claim 10 in which said annular apex is positioned
less than one inch from the outermost portion of said bucket lip,
and said annular apex is essentially linear.
14. The bucket of claim 10 in which the surfaces of said inwardly
projecting ridge extending from the annular apex to the interior
wall of the bucket are concave in shape.
15. The bucket of claim 14 in which a bucket lid is sealingly
secured to the lip of said bucket, the lip of said bucket being
retained in a locking slot defined by inner and outer annular walls
of said bucket lip, the inner annular wall also carrying an
outwardly positioned annular projection defining a surface which
faces the annular locking slot which defines an angle to the plane
of said inner annular wall, said annular projection being in
contacting and retaining relation with a mating projection of said
bucket lip positioned within the locking slot, the inner walls also
defining, below said outwardly-positioned annular projection, a
surface which is of a shape complimentary to the shape of the side
of the annular ridge which faces the mouth of said bucket, to form
an annular, abutting, sealing surface between said outer side of
the ridge and outer wall, and extending essentially to said apex,
said outer annular wall defining an inwardly-positioned projection
adapted to interlock with said annular projecting ridge, positioned
within the locking slot.
16. A plastic bucket lid for attachment to the lip of a plastic
bucket, said lid defining first, second and third transversely
extending annular walls, the first and second annular walls forming
between them an annular open depression, said second and third
annular walls defining an annular locking slot outside of said
depression and adapted to retain a plastic bucket lid in locked,
sealingly secured relation, the first annular wall constituting an
integral segment of the bucket lid, being connected at opposed
sides to other portions of the bucket lid, said first annular wall
being of less thickness than the second annular wall to facilitate
preferential flexing by the first annular wall upon shock adjacent
the bucket lip, causing said second wall to remain relatively
immovable under such circumstances for improved sealing
strength.
17. The bucket of claim 16 in which the second annular wall carries
an outwardly-positioned annular projection defining a surface which
faces the annular locking slot and which defines an angle of
80.degree. to 100.degree. to the plane of said second annular wall,
said annular projection being adapted for contacting and retaining
relation with the mating projection of said bucket lip positioned
within said locking slot.
18. The plastic bucket lid of claim 17 in which said third annular
wall defines an inwardly positioned projection adapted to interlock
with an outwardly facing projection of said bucket lip positioned
within the locking slot.
19. The plastic bucket of claim 18, carrying a lip of a plastic
bucket within said locking slot, the interior wall of said bucket
defining an annular, inwardly projecting ridge positioned adjacent
to but spaced from said lip, said ridge extending around the inner
circumference of said bucket and defining an annular,
inwardly-pointed apex, said second wall defining a surface which is
in intimate engagement with the side of said projecting ridge
extending from adjacent said apex toward the bucket lip.
Description
BACKGROUND OF THE INVENTION
In the application cited immediately above, lids for paint buckets
and cans are disclosed which may be removed by prying an outer
flange of the lid off of the bucket lip with a screwdriver or the
like in an easy manner, yet which, when locked on the bucket lip,
are very resistant to accidental opening due to shock of dropping
or the like.
In accordance with this present invention, an improved bucket is
disclosed, which bucket may be used in conjunction with lids of the
type disclosed in previous application, or with other lids as well,
to obtain improved, sealed containers for paint or other materials,
which particularly may have the advantage of being processable on
the current, industrial automated paint can filling and sealing
machinery. At the same time, the same major advance of sealing
strength of the joined bucket and lid as found in the previously
cited application may be achieved in accordance with this
invention.
DESCRIPTION OF THE INVENTION
In this invention, a plastic bucket is provided having a lip at its
mouth, with the lip defining means for engaging a bucket lid in
sealingly secured relation to the lip.
In accordance with this invention, the interior wall of the bucket
defines an annular, inwardly projecting ridge positioned adjacent
to but spaced from the lip. The ridge extends around the inner
circumference of the bucket, and defines an annular, inwardly
pointed apex. Advantages of this are to provide increased hoop
strength to the bucket adjacent to its mouth, while at the same
time the annular ridge can be utilized as an antisplashing and an
internal brush wiping member within the bucket, which can greatly
reduce the spillage of paint or the like from the bucket during
use.
Preferably, the annular apex is positioned less than one inch from
the outermost portion of the bucket's lip, typically about one
quarter inch or so. It is also preferable for the annular apex to
be thin enough to be characterized as essentially linear, for
improved brush wiping characteristics.
Furthermore, the surfaces of the inwardly-projecting ridge
extending from the annular apex to the interior wall of the bucket
are preferably concave in shape, especially the surface between the
apex and the bucket lip.
The lid used on the bucket preferably defines first and second
transversely positioned annular walls forming an annular, open
depression, with the second annular wall defining the outer limit
of the depression. The first annular wall defines the inner limit
of the depression, and is preferably an integral segment of the
bucket lid, being connected at opposed sides to other portions of
the bucket lid.
A third annular wall of the lid may be positioned outwardly from
the second annular wall, with the second and third annular walls,
in turn, defining between them an annular locking slot which
receives and holds the lip of the bucket. The second wall also may
carry an outwardly positioned annular projection defining a surface
which faces the annular locking slot and which may define an angle
(for example about 80.degree. to 100.degree.) to the plane of the
second annular wall. This annular projection is intended for
contacting and retaining relation with a mating projection of the
bucket lip positioned within the locking slot.
The second wall also defines, below the outwardly-positioned
annular projection, a surface which is of a shape complimentary to
the shape of the side of the annular ridge which faces the mouth of
the bucket. As a result of this, an annular abutting, sealing
surface may be formed between the upper side of the ridge and the
second wall, extending essentially to the annular apex, for
improved sealing of the container.
Also, the third annular wall may define an inwardly positioned
projection adapted to interlock with an outwardly facing projection
of the bucket lip, positioned within the locking slot, for
additional sealing of the two components.
It is also preferred for the first annular wall of the bucket lid
to be adapted for preferentially flexing upon stress or shock
adjacent to the bucket lip, as described in the previously cited
application, with the result that the second annular wall can
remain relatively immovable under such circumstances for improved
sealing strength.
The second annular wall may be thicker than the first annular wall,
which assists the preferential flexing of the first wall.
Preferably, the mating surface of the second wall bearing against
the inwardly-projecting ridge is of convex shape to match the
preferably concave shape of the upper side of the
inwardly-projecting ridge.
Furthermore, if desired, the bucket lip can also define an annular,
outwardly projecting ridge extending around the outer circumference
of the bucket lip, and defining an annular, outwardly pointing
apex. A surface of the bucket lip may extend outwardly relative to
the direction of the bucket mouth from said apex, being of
generally planar, annular shape. The generally planar, annular
surface of the outer end of the bucket lip is preferably free of
mold parting line marks for improved sealing characteristics, with
the mold parting line being preferably positioned at the
outwardly-pointing annular apex of the bucket lip. This improves
the sealing characteristics of the container, and is rendered
possible because the shape of the generally planar annular surface,
and the inner surface of the bucket lip may be appropriately
proportioned to facilitate their removal from a mold, even though
the parting line is positioned at the annular outwardly-pointing
apex.
As a further aspect of this invention, apparatus for removing of
molded bucket from a mold core is disclosed, which comprises pusher
means for pressing against the bucket interior and optional
pneumatic means for pressurizing the bucket interior to facilitate
its longitudinal removal from the core.
In accordance with this invention, pressurized fluid supply means
are provided, along with channel means communicating through the
mold core between the pressurized fluid supply means and the
inwardly-projecting annular ridge of a bucket as previously
described. Thus, a supply of pressurized fluid is provided to
circumferentially expand the plastic bucket adjacent the ridge, to
facilitate its removal from the core by the pusher means and
pneumatic pressure.
The pressurized fluid supply channel means is of sufficiently
narrow dimension to prevent the inflowing of liquid molding
compound into it during the molding operation. For example, the
fluid supply channel means may have a width essentially of 0.0005
to 0.002 inch.
Referring to the drawings, FIGS. 1 and 2 are perspective views of
differing buckets and lids utilizing this present invention.
FIG. 3 is an enlarged, fragmentary, longitudinal sectional view of
a portion of the bucket and lid in accordance with FIG. 1.
FIG. 4 is an enlarged, fragmentary, longitudinal sectional view of
the bucket and lid of FIG. 2.
FIG. 5 is a longitudinal sectional view of a mold core for the
manufacturing of the bucket of FIG. 1, shown in the configuration
where the bucket has been newly-formed on the mold core.
FIG. 6 is a longitudinal sectional view of the mold core and bucket
of FIG. 5, showing the bucket in the process of being removed from
the mold core.
FIG. 7 is a greatly enlarged longitudinal sectional view, showing
the lip of the bucket of this invention and its relationship with
the mold core.
Referring to FIG. 1, a straight-walled bucket 10, suitable for
processing with industrial paint bucket filling machinery, is
shown, carrying a lid 12. Both bucket 10 and lid 10 are made of
single, molded pieces of thermoplastic material.
Alternatively, this invention can be used as shown in FIG. 2 with a
tapered bucket 12 and its lid 14 which, along with the bucket of
FIG. 1, can be made to any of the designs of bucket lip and closure
system disclosed herein, or designs equivalent thereto.
Referring to FIG. 3, the design of bucket closure utilizes the
principles of the previously-cited application Ser. No. 963,736,
although lid 12 is shown to be free of the optional radial vanes in
the specific embodiments disclosed therein, since for the specific
embodiment disclosed, for use as a paint bucket, such vanes are not
found to be required.
Bucket 10 defines an annular lip 16, having an enlarged upper end
as shown.
Lid 12 defines first annular wall 18 and second annular wall 20
which, in turn, defines annular open depression 22 in which the
radial vanes may be added if desired.
A third annular wall 24 of lid 12 may be positioned outwardly from
second annular wall 20, which wall, in turn, defines with wall 20
the annular locking slot in which lip 16 is shown to reside, with
lip 16 being received and held therein.
Second wall 20 also carries the outwardly-positioned annular
projection 26, defining a surface 28 which faces annular locking
slot 16, and which may desirably define an angle of essentially
80.degree. to 100.degree. to the plane of second annular wall 20.
This annular projection 28 is shown to be in contacting and
retaining relation with mating projection 30 of bucket lip 16,
positioned within the locking slot.
In accordance with this invention, bucket 10 defines an annular,
inwardly projecting ridge 32, positioned adjacent to but spaced
from lip 16. Ridge 32 extends around the inner circumference of
bucket 10 and defines an annular, inwardly pointed apex 34. As
stated previously, ridge 32 provides hoop strength to the bucket
adjacent its mouth, and provides an internal brush-wiping member
within the bucket.
Furthermore, annular ridge 32 serves as a splash guard to inhibit
the splashing of the contents of the open bucket 10 out of the
mouth thereof, since inwardly projecting ridge 32 tends to direct
any slashing or splashing paint radially inwardly toward the center
of the bucket where it can fall back and rejoin the bucket contents
without spilling. Specifically, the apex 34 of ridge 32 may be
positioned about 1/8 or 3/16 inch from the upper surface 36 of
bucket lip 16.
Surfaces 38, 40 of annular ridge 32 are preferably concave, surface
38 being shaped to match the corresponding surface 42 of second
wall 20, positioned below the surface 28 of the annular projection
to provide an annular, mating, sealing surface between walls 38,
42, preferably extending essentially to apex 34. Accordingly, an
extensive seal is provided between bucket lip 16 and lid 12,
beginning adjacent to apex 34 and extending through the cross
sectional area about the surface of lip 16 up to and beyond the top
surface 36 of lip 16. As the result of this, the bucket and lid of
this invention provide excellent sealing characteristics, while at
the same time exhibiting great resistance to accidental removal of
the lid by shock imparted through dropping of the bucket or the
like.
First wall 18 may define the outer part of an annular depression
44, with annular innermost wall 46 defining the inner wall of the
depression 44. Accordingly, upon application of stress force to the
bucket and lid of FIG. 3, wall 18 preferentially flexes, absorbing
the shock force without displacement of wall 20 or wall 24, so that
the seal of the bucket lip 16 remains intact.
Preferably, the second annular wall 20 of lid 12 is of greater
thickness than first annular wall 18, which facilitates the
selective flexing of first annular wall 18 upon application of
shock to the closed bucket lid, while walls 20 and 24 remain in
relatively rigid, gripping relation to bucket lip 16.
Referring to FIGS. 2 and 4, a tapered bucket 13 is shown, in
contrast to straight walled bucket 10, as well as a modification of
the closure of this invention. Nevertheless, either type of
closure, or further modification thereof, may be used
interchangeably on straight-walled or tapered buckets.
As in the previous embodiment of FIG. 3, FIG. 4 shows a bucket
defining a lip 16a, with bucket lid 14 attached thereto. Lid 14
defines first wall 18a and second wall 20a of a shape similar to
the previous embodiment, with the exception that the central
portion 44 of lid 14 remains in depressed relationship relative to
the peripheral portion of lid 14 shown in FIG. 4, because no wall
corresponding to wall 46 is present. This optional variation still
provides wall 18a, which can selectively flex in a preferential
manner to wall 20a, but with the bulk of the lid at the central
portion 44 occupying a plane including a lower portion of wall 20a
rather than an upper portion of the corresponding wall 20 as in
FIG. 3.
Third annular wall 24a is provided for a similar function as in the
previous embodiment. Annular, inwardly projecting ridge 32a may be
of similar design and purpose as annular ridge 32.
In this embodiment, bucket lip 16a defines an outwardly-pointing
annular ridge 46, which terminates in an outwardly pointing annular
apex indicated at the same reference numeral. The surface 48 of the
bucket lip, which extends outwardly from apex 46 relative to the
direction of the bucket mouth, defines a generally planar annular
surface which is adapted, relative to the shape of the inner
surface 50 of bucket lip 16a, to permit the parting line for the
bucket lip to be located at a position other than the generally
planar surface 48 and the outer end 52 of bucket lip 16a.
Specifically, the parting line created on bucket lip 16a by the
mold in which it is manufactured may be located at apex 46, so that
the annular surfaces 48 and 52 can be smooth and unblemished for
maximal sealing characteristics of section 54 of bucket lid 14,
bearing tightly against surfaces 48 and 52.
In the embodiment of FIG. 3, parting line 56 is often placed on
bucket lip 16 as an annular line at the outer end 36 of lip 16. It
may be more desirable in many circumstances to move the parting
line to annular apex 46, while the specific shape of bucket lip 16a
facilitates the easy and reliable removal of lip 16a from its mold,
even when the parting line is located away from the outer end of
lip 16a, for example, at apex 46.
Annular projections 58, 58a on the exterior of buckets 10, 13,
adjacent the respective lips, are provided as a barrier to abut
against the respective outer walls 24, 24a in the event of heavy
flexing of the container, to serve as an added support member
against pop-off of the lid.
Referring to FIGS. 5 through 7, mold core apparatus for the
manufacture of particularly a straight-walled bucket such as bucket
10 of this invention is shown. The corresponding mold which
surrounds mold core 60 during the molding operation is not shown,
but may be of conventional design.
A pneumatic bucket removal means is shown, in which ridge 32, 32a
of a straight-walled bucket serves as a pressure-maintaining gasket
impinging against the mold core as the bucket is removed therefrom
by pressured air.
Mold core 60, which has separated from a mold cavity half, exposes
the freshly-molded bucket 10 positioned about its exterior.
Pusher means 62 comprises a shaft for pressing against the bucket
interior, for assisting in removal of the bucket from core 60. As
shown, shaft 62 may be only about 3/8 of an inch in diameter and
serves to assure the proper removal of the bucket from the core in
automated operation. A great portion of the removing force is
provided by pneumatic means as described below.
Shaft 62 reciprocates in a chamber 64 defined in mold core 60, with
the inner end of shaft 62 defining a piston head 66. Chamber 64 is
closed at its lower end by means of seal 68.
O-rings 70, 72 are provided respectively about the periphery of
piston member 66, and shaft 62 at the upper end of chamber 64.
Inlet air pressure line 73 communicates with the lower portion 74
of chamber 64, to impel rod 62 outwardly by pressurized air,
forcing bucket 10 off of mold core 60. Pressurized air conduit 76
is provided to cause piston 66 and shaft 62 to withdraw by
pressurization of upper portion 78 of chamber 64, so that shaft 62
can reciprocate back and forth for bucket molding removal
operation.
Pneumatic line 80 communicates with cylindrical channel 82 in mold
core 60, in which shaft 62 reciprocates. The upper portion 84 of
rod 62 is positioned in closer tolerance to the diameter of channel
82 than the lower portion, so that sealing action against the
pressurized air from conduit 80 is provided when rod 62 is in its
retracted position. However, when rod 62 begins to advance, a
larger flow conduit for air from line 80 is thus provided, to flow
into the space between bucket 10 and mold core 60. The pressurized
air tends to urge the bucket to slide outwardly off of the mold
core.
Fourth pneumatic line 86 communicates with an annular recess 88 in
mold core 60, which recess is positioned to receive the annular
inwardly extending ridge 32 of bucket 10 as shown in FIG. 7.
Annular recess 88 contains a ring member 90, which may be a split
ring made of material cut away from the remainder of core 60 to
make the annular recess 88 in the first place, and then reattached.
Split ring 90 is reattached within annular recess 88 to define flow
paths 92, 94 about the inner peripheries of split ring 90, with
flow paths 92, 94 being preferably generally annular in shape, with
the exception of necessary support members 96, which are
intermittently positioned to support and carry split ring 90, with
the flow paths 92, 94 surrounding support member 96 to permit free
flow of air through the flow paths about the support members
96.
Preferably, annular flow channels 92, 94 have a width or thickness
of essentially 0.0005 to 0.002 inch, typically 0.001 inch, with
their optimum thickness depending upon the viscosity of the molding
compound and the pressure of molding. It is preferred to select a
thickness which is sufficient to allow the flow of air into the
inner surface area 102 of bucket 10 while at the same time being
sufficiently narrow that molding compound is incapable of flowing
significantly into the air supply channels 92, 94 during the
molding process.
Accordingly, to facilitate the removal of lip 16 of bucket 10 from
the mold core, pressurized air can pass through conduit 86 into
annular manifold 98, from where it can flow into generally annular
flow paths 92, 94 about the inner peripheries of split ring 90.
From there, the air enters into contact at apertures 100 with the
inner surface of bucket 10 providing flowing pressurized air to the
general area of inner bucket surface 102 which abuts split ring 90
and related portions of mold core 60.
Split molding ring 104 (FIG. 5), which is utilized in the molding
process for the formation of the outer surface of lip 16 of the
bucket 10, is retracted during the bucket removal step of the
molding operation, as shown in FIG. 5. Accordingly, upon
pressurization of flow channels 92 and 94, lip 16 and inner annular
projection 32 of bucket 10 can be forced outwardly by stretching
through the action of the pulse of pressurized air. At the same
time, as shown in FIG. 6, pressurized air passing through line 80
blows bucket 10 outwardly off of the mold core, with facilitated
action since lip 16 and annular projection 32 are at least
partially out of the annular recesses of the mold core which
defines them during the molding process.
Typically, the air pressure in each of lines 73, 76, 80 and 86 may
range between 80 to 120 psi., with a typical pressure being about
100 psi. However, the respective pressures of each line may be
adjusted as desired for optimum results in each specific molding
situation.
While a large variety of molding compounds may be used in
accordance with this invention, one specific and successful molding
compound is the polyethylene resin sold by the Dow Chemical Company
as No. 12065. If desired, from two to six percent by weight of a
microbead glass filler may be added for strengthening of the resin
material.
In accordance with this invention, a plastic bucket is provided
having an annular inwardly projecting ring near its lip which
serves both as a splash retarding ring and a brush wiping member,
and also serves to increase the hoop strength of plastic buckets.
By this invention, these buckets may be easily molded on a
non-collapsible core, even when the buckets are of straight-walled
characteristics, using a simple, non-collapsible core if desired
for efficient, rapid molding operation with a mold that needs
little maintenance.
The above has been offered for illustrative purposes only, and is
not intended to limit the invention of this application, which is
as defined in the claims below.
* * * * *